If it's Windows and you don't want any bells or whistles, try Windows Media player 6 or 7.
If you're using Windows XP you will have WMP 9 or 10 anyway, but WMP6/7 is still on your system. Just do a search for mplayer.exe or mplayer2.exe.
It is a simple no nonsense media player.
I just bought a used laptop, so being a few years old, it can barely handle itunes for music and not at all for video. what is a good, low resource media player i can use? the laptop is a dell c400 1.2 ghz, 256mb ram, 20gb hdd. also, if this makes any difference, i us it mostly to play music from my networked desktop.